# driving high-side N-channel MOSFETs in H-Bridge

What is the most efficient / best way to make an H-bridge? I want low power loss but also fast switching time since I will using PWM. I have considered using 2 P-channel and 2 N-channel MOSFETs to make this. But, I realized that P-channel devices have a much higher channel resistance causing more power loss.

So, I was considering using 4 N-channel MOSFETs but the problem lies with the gate voltage. My power source will be approximately 15V and I am going to be using a arduino/atmega for PWM signal (5V). So, I am wondering what is the best way to amplify this gate voltage so that the high side N-channel MOSFETs turn on while also giving me a rapid switch time. Or, am I digging a hole for myself and should just stick with a P-channel?

• possible duplicate of driving low side of a mosfet bridge with 3.3V – Phil Frost Aug 6 '13 at 13:58
• There are really at least three problems here, each complex enough to merit separate questions: 1) driving MOSFETs in parallel, 2) using N-channel MOSFETs for the high side, and 3) designing a proper gate driver to switch MOSFETs quickly. If the general answers already here don't address your question, I'd suggest you edit or ask a new one to be more specific. – Phil Frost Aug 6 '13 at 14:06
• How much current? What sort of switching speeds are you talking about? Have you considered an integrated solution (IC)? – Tut Aug 6 '13 at 14:19
• I'm not being sarcastic, it seems from your wording you don't know these exist. Gate Driver IC's – Matt Aug 6 '13 at 14:51
• @Matt Anderson I think if you are not being sarcastic you are at least not helping so much. Gate driver ICs are not a standart, and have many pros and cons, as having so much types of implementation too. For a infinity on-time of the high-side switch, a boot-strap gate drive IC, will not work (only if using a isolated supply for the high side, so no bootstrap will be used). – Diego C Nascimento Sep 11 '13 at 10:02

I pressume that by power loss, you refering to the power dissipation on the transistors.

So in this case, P-channel MOSFETs have high on-resistence, so its common for high current applications to use N-channel at the top of the bridge too.

To drive the top transistors, you have some options. Some of then:

• Pulse-transformers
• Gate-drive IC's that can be of different topology's like boot-strapping.
• Isolated power supply with level-shifter
• Isolated power supply with Opto-isolators

All with their characteristics.

Some good app-note http://www.ti.com/lit/ml/slup169/slup169.pdf

On my point of view, you could select a pre-driver to drive the H-bridge. As I know, Infineon has a lot of ICs to solve your problem. And if you want to design a low power loss circuits, you'd better forcus on your Mosfet's Rdson and Qg. P-channel is not recommended. Because its high Rdson.